Sensing and responding to changes in the environment is a hallmark of living systems, and a major challenge of systems biology is to understand the biological networks that connect sensory information to behavioral responses. We are interested in how biochemical and neuronal networks encode and process sensory information to produce adaptive locomotory behavior, and how this behavior benefits the organism in their natural environment. We study the sensory behavior of two model organisms, E. coli and C. elegans. These organisms can sense the world as we do. They use their sense of smell to find their way to food (chemotaxis) or use temperature measurements to move to cooler areas when things get too hot (thermotaxis). We study E. coli because it is a model of how biochemical networks process sensory information in single cells. Discovering how bacteria measure and process this information will likely reveal some design principles of networks in all cells. C. elegans is a nematode that gets through life with a surprisingly small number of neurons (~ 300), and so it is an excellent model of how small neuronal networks process sensory information. Its compact neuronal network may allow us to understand complete sensory pathways from sensory neuron to motor output. Using the worm system, we hope to understand the processing of “complex” stimuli like thermal pain. Our work is interdisciplinary. We use a combination of techniques that span the areas of genetics, physiology, photonics, and biological physics. We also work hard to develop new instrumentation and computational tools.